Patient-Specific Implants: Seven Things You Should Know

In a world where almost everything can be made to order, should patients' orthopedic implants be as well? Corey Wilson-Wirth, director of advanced technology at Tornier, a designer, manufacturer, and marketer for joint replacement and soft tissue repair devices weighed in on the topic at MEDevice San Diego. He offered some of the very real benefits for patient-specific implants but says the implants are also facing some big challenges as the market moves ahead.

1.) Patient-Specific Implants Offer Better Quality

The production cycle of a patient-specific implant works like this: After a doctor prescribes an implant, the hospital will order a CT scan of the patient and send the data to the manufacturer. The manufacturer in turn creates a CAM code for the implant, the doctor approves the virtual surgical plan, and the implant is manufactured, sterilized, and shipped to the hospital for implantation.

"The process offers a simpler instrumentation system with fewer steps,” Wilson-Wirth says. With so much going into the planning phase there is potential for more accurate implant placement, pre-op corrections (such as varus misalignment) can be done in the planning phase, which adds up to potentially shorter surgery time. “There is also a potentially lower risk of infection because all of the instruments involved are single use,” Wilson-Wirth says.

2.) Saving Money for Hospitals and Device Companies

Since patient-specific implants are one-offs there is less inventory for hospitals to manage. “They're not worrying about banks of implants being brought into the case,” Wilson-Wirth says. Device companies can also benefit from this smaller inventory. “[Orthopedics] is a very capital and inventory intensive business. Every dollar of inventory you can free up is a dollar for R&D and other activities.”

Lower inventory also means lower demand for sterilization cycles between cases – further lowering costs. There is also faster OR turnover since doctors do not have a variety of implants to test and choose from.

The iTotal Knee by Conformis is a patient-specific knee implant.

3. ) Comfortable

Patient-specific implants offer a matched geometry to the patient and no implant over- or underhang, which in turn can lead to pain for the patient, or can mean less blood loss during the procedure. Off-the-shelf (OTS) implants, by contrast, can often have an unnatural feel for the patient.

4.) Patient-Specific Implants are Labor Intensive for Manufacturers

Custom, one-off implants means production runs of exactly one unit (as opposed to hundreds with OTS implants). From a device company standpoint this means additional manpower and overhead associated with the intakeprocess. “Frankly one of the bigbest labor intensive steps that's added is that process to convert patient data into manufacturing inputs,” Wilson-Wirth says. “It's still a relatively manual process, where you have a person sitting at a CAD terminal.”

Manufacturing a one-off device likely means one-off tooling as well since every patient is a little bit different. And, of course, these tools can only be used once, then discarded.

5.) Hospitals Have Limited Contingencies

One implant means one chance to get it right. “There are limited contingencies in OR,” Wilson-Wirth says. “If a device gets damaged there's not a backup.”

There are also radiology logistics to consider for hospitals, who may need to train and certify employees on how to properly create and send scans to manufacturers.

6.) Software Updates Can Be an Issue

Converting the CT data for manufacturers requires software that is FDA regulated. If the software changes it needs to be submitted to FDA for re-evaluation and possibly even a whole new 510(k) process. It's easy to imagine how this can gum up the production cycle.

7.) OTS is readily available

Right now if a doctor wants an OTS implant she can get one almost immediately. Not at all true for patient-specific implants yet. As such manufacturers of patient-specific implants are under huge pressure to have a quick turnaround. “My understanding is that companies are turning implants out comfortably in 5-6 weeks and getting it down to 4 weeks,” Wilson-Wirth says. “But again, you’re competing with something that's ready to go.”

Wilson-Wirth concluded that improved automation would be key in solving many of the issues surrounding patient-specific implants. “Anything that can be done to automate the process of converting data will help to decrease turnaround and hopefully make it more cost effective,” he says. He also hopes that advances in 3-D printing could eliminate production tooling and shorten turnaround. However, the technology needs further refinement in tolerance and surface finish for this to be realistic.

Also, while there are studies confirming the benefits and efficacy of patient-specific implants Wilson-Wirth says that the literature to date is mixed. ”We will need more studies and longer-term survivorship data for best perspective.”